Page 57 - Engineering Rock Mass Classification_ Tunnelling, Foundations and Landslides
P. 57
Poor Boring Medium 0.6 to 1.2 m 0.9 to 1.5 m
circular
RQD 25 to 50 machine
Very poor Drilling and Medium 0.2 to 1.2 m 0.6 to 1.2 m
RQD <25 blasting to heavy 0.6 m 0.6 to 1.2 m
circular
Boring 0.9 m
machine Medium 0.6 to 0.9 m
to heavy
circular
Drilling and Heavy 0.6 m
blasting circular
Very poor Both methods Very 0.6 m
squeezing heavy
and swelling circular
ground
Source: Deere et al., 1970.
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